This invention relates to smoking articles such as cigarettes and little cigars having self-extinguishing properties when laid on a flat surface yet will not extinguish when held in the hand or placed in an ashtray. For many years, attempts have been made to design a cigarette with such self-extinguishing properties but none has resulted in a cigarette acceptable to the consumer.
Cigarettes have been recognized to be a great safety problem for many years. It has been reported that a patent for a self-extinguishing cigarette was first issued in 1854 and about one hundred other patents have been issued since then. The safety problem continues because the claimed self-extinguishing feature either does not work or the "solution" has been impractical.
Approaches to the control of the fire hazards of burning cigarettes have involved various schemes.
U.S. Pat. No. 3,183,914 discloses the use of an intumescent material as a constituent of the tobacco filler. High water content sodium silicate having a weight ratio of sodium monoxide:silicon dioxide within the range of 2:1 to 1:4, in the form of granules, is mixed with the tobacco. The granules preferably should have a mesh size of 50 to 65 and, depending upon mesh size, the tobacco mixture may comprise up to 50% by weight of silicate, the silicate percentages being greater for larger particles and less for finer particles. Preferably, the tobacco-silicate mixture contains less than 25% silicates. The silicates can also be applied to the tobacco in solution form in drops. A considerably lower percentage of silicate solution by weight is added than when added in granular form silicates. When the cigarette is smoked, the sodium silicate foams up and forms a hard insulating mass interspersed with tobacco ashes accompanied with a release of the water of hydration. The fused silicate prevents dropping of tobacco ash and also acts as an insulator to prevent burning of any surface, such as furniture, on which the cigarette may be placed. Thus, it is clear that the burning cigarette is not actually extinguished but the burning zone is insulated from the substrate.
U.S. Pat. No. 4,230,131 relates to the use of flame-retardants as additives to the tobacco and/or the paper of cigarettes. Additives include boric acid and benzenephosphoric acid in a range of 2.5 to 5.5 weight percent of the tobacco. The resulting cigarettes self-extinguished when left unattended within approximately two minutes.
U.S. Pat. No. 4,452,259 relates to a smoking article (cigarette) having at least one circumferential self-extinguishing band printed at about the center of the cigarette, the band containing a substance which is liquid in the temperature range of 100.degree.-200.degree. C. and which, as the burning cone comes into contact, forms a fluid film on the cigarette paper to restrict the flow of air to the burning cone to extinguish the cigarette within 2 to 5 minutes when it is not being actively puffed.
U.S. Pat. No. 4,146,040 relates to a fire resistant cigarette in which the wrapper is coated in separate steps with solution based coatings of an alkali metal silicate and a pH lowering material. The cigarettes are fire resistant in accordance with Federal test method DOC-FF-4-72 (Flammable Fabrics Act).
U.S. Pat. No. 4,187,862 approaches cigarette hazards by coating, in one or two operations, from 40 to 100% of the cigarette paper surface area with alkali metal silicate solutions, using SiO.sub.2 as the principal fire retardant, resulting in a cigarette which will not self-extinguish when held in a horizontal position for one minute. The cigarettes are reported to pass a fire safety test derived from the Federal Flammability Standards For Mattresses, Fed. Register, Vol. 37, No. 110, June 7, 1972.
U.S. Pat. No. 4,453,553 relates to the selection of and treatment of low porosity cigarette wrapper with water or ethyl alcohol to reduce sidestream smoke and by depositing linear burn rate reducing cigarette wrapper substance on the paper selected from the group consisting of citric acid, magnesium citrate, magnesium acetate, tartaric acid, lactic acid, a sugar, non-fat milk and skim milk to impart fire resistance to the cigarette.
U.S. Pat. No. 3,220,418 relates to a cigarette having a non-combustible sheath wrapped around and in spaced relationship to the cigarette. The sheath retains the ashes and prevents the burn zone from contacting any combustible material. The sheath or the cigarette wrapper has applied thereto an intumescent water soluble alkali metal silicate which, upon intumescence, separates the wrapper and sheath to provide passageways for combustion air to the cigarette.
U.S. Pat. No. 3,528,432 discloses a cigarette with a flame-proofed insert which inhibits propagation of combustion. The insert is flame-proofed by a coating or impregnant of an ammonium salt of a metal-amido-polyphosphate complex.
U.S. Pat. No. 3,702,117 discloses cigarettes with flammability barriers or discs formed from specially prepared tobacco by compression into relatively thin flat discs disposed along the length of the cigarette which will extinguish an unattended cigarette. The discs are preferably treated with an impregnant selected from cottonseed oil, degras, lard and tallow to assure that the cigarette will continue to burn while being actively smoked.
U.S. Pat. No. 3,985,143 discloses self-extinguishing cigarettes having a small sack or container of water which is ruptured by the advancing burning tobacco thus extinguishing the cigarette.
Notwithstanding the essentially continuous and varied efforts over the decades to solve the fire-safety problem of cigarettes, the problem continues unabated. An effort to officially address the problem of cigarette safety is evidenced by the Cigarette Safety Act of 1984 (P.L. 98-567; 98 Stat. 2925, Oct. 30, 1984), which established the Technical Study Group on Cigarette and Little Cigar Fire Safety "to determine the technical and commercial feasibility, economic impact, and other consequences of developing cigarettes and little cigars that will have a minimum propensity to ignite upholstered furniture or mattresses."